Source code
Revision control
Copy as Markdown
Other Tools
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
#include "vm/ConcurrentDelazification.h"
#include "mozilla/Assertions.h" // MOZ_ASSERT, MOZ_CRASH
#include "mozilla/RefPtr.h" // RefPtr
#include "mozilla/ReverseIterator.h" // mozilla::Reversed
#include "mozilla/ScopeExit.h" // mozilla::MakeScopeExit
#include <stddef.h> // size_t
#include <utility> // std::swap, std::move, std::pair
#include "ds/LifoAlloc.h" // LifoAlloc
#include "frontend/BytecodeCompiler.h" // DelazifyCanonicalScriptedFunction, DelazifyFailureReason
#include "frontend/CompilationStencil.h" // CompilationStencil, ExtensibleCompilationStencil, BorrowingCompilationStencil, ScriptStencilRef
#include "frontend/FrontendContext.h" // JS::FrontendContext
#include "frontend/ScopeBindingCache.h" // StencilScopeBindingCache
#include "frontend/Stencil.h" // TaggedScriptThingIndex, ScriptStencilExtra
#include "js/AllocPolicy.h" // ReportOutOfMemory
#include "js/experimental/JSStencil.h" // RefPtrTraits<JS::Stencil>
#include "vm/JSContext.h" // JSContext
#include "vm/StencilCache.h" // DelazificationCache
using namespace js;
bool DelazifyStrategy::add(FrontendContext* fc,
const frontend::CompilationStencil& stencil,
ScriptIndex index) {
using namespace js::frontend;
ScriptStencilRef scriptRef{stencil, index};
// Only functions with bytecode are allowed to be added.
MOZ_ASSERT(!scriptRef.scriptData().isGhost());
MOZ_ASSERT(scriptRef.scriptData().hasSharedData());
// Lookup the gc-things range which are referenced by this script.
size_t offset = scriptRef.scriptData().gcThingsOffset.index;
size_t length = scriptRef.scriptData().gcThingsLength;
auto gcThingData = stencil.gcThingData.Subspan(offset, length);
// Iterate over gc-things of the script and queue inner functions.
for (TaggedScriptThingIndex index : mozilla::Reversed(gcThingData)) {
if (!index.isFunction()) {
continue;
}
ScriptIndex innerScriptIndex = index.toFunction();
ScriptStencilRef innerScriptRef{stencil, innerScriptIndex};
if (innerScriptRef.scriptData().isGhost() ||
!innerScriptRef.scriptData().functionFlags.isInterpreted()) {
continue;
}
if (innerScriptRef.scriptData().hasSharedData()) {
// The top-level parse decided to eagerly parse this function, thus we
// should visit its inner function the same way.
if (!add(fc, stencil, innerScriptIndex)) {
return false;
}
continue;
}
// Maybe insert the new script index in the queue of functions to delazify.
if (!insert(innerScriptIndex, innerScriptRef)) {
ReportOutOfMemory(fc);
return false;
}
}
return true;
}
DelazifyStrategy::ScriptIndex LargeFirstDelazification::next() {
std::swap(heap.back(), heap[0]);
ScriptIndex result = heap.popCopy().second;
// NOTE: These are a heap indexes offseted by 1, such that we can manipulate
// the tree of heap-sorted values which bubble up the largest values towards
// the root of the tree.
size_t len = heap.length();
size_t i = 1;
while (true) {
// NOTE: We write (n + 1) - 1, instead of n, to explicit that the
// manipualted indexes are all offseted by 1.
size_t n = 2 * i;
size_t largest;
if (n + 1 <= len && heap[(n + 1) - 1].first > heap[n - 1].first) {
largest = n + 1;
} else if (n <= len) {
// The condition is n <= len in case n + 1 is out of the heap vector, but
// not n, in which case we still want to check if the last element of the
// heap vector should be swapped. Otherwise heap[n - 1] represents a
// larger function than heap[(n + 1) - 1].
largest = n;
} else {
// n is out-side the heap vector, thus our element is already in a leaf
// position and would not be moved any more.
break;
}
if (heap[i - 1].first < heap[largest - 1].first) {
// We found a function which has a larger body as a child of the current
// element. we swap it with the current element, such that the largest
// element is closer to the root of the tree.
std::swap(heap[i - 1], heap[largest - 1]);
i = largest;
} else {
// The largest function found as a child of the current node is smaller
// than the current node's function size. The heap tree is now organized
// as expected.
break;
}
}
return result;
}
bool LargeFirstDelazification::insert(ScriptIndex index,
frontend::ScriptStencilRef& ref) {
const frontend::ScriptStencilExtra& extra = ref.scriptExtra();
SourceSize size = extra.extent.sourceEnd - extra.extent.sourceStart;
if (!heap.append(std::pair(size, index))) {
return false;
}
// NOTE: These are a heap indexes offseted by 1, such that we can manipulate
// the tree of heap-sorted values which bubble up the largest values towards
// the root of the tree.
size_t i = heap.length();
while (i > 1) {
if (heap[i - 1].first <= heap[(i / 2) - 1].first) {
return true;
}
std::swap(heap[i - 1], heap[(i / 2) - 1]);
i /= 2;
}
return true;
}
bool DelazificationContext::init(const JS::ReadOnlyCompileOptions& options,
const frontend::CompilationStencil& stencil) {
using namespace js::frontend;
RefPtr<ScriptSource> source(stencil.source);
DelazificationCache& cache = DelazificationCache::getSingleton();
if (!cache.startCaching(std::move(source))) {
return false;
}
auto initial = fc_.getAllocator()->make_unique<ExtensibleCompilationStencil>(
options, stencil.source);
if (!initial || !initial->cloneFrom(&fc_, stencil)) {
return false;
}
if (!fc_.allocateOwnedPool()) {
return false;
}
if (!merger_.setInitial(&fc_, std::move(initial))) {
return false;
}
switch (options.eagerDelazificationStrategy()) {
case JS::DelazificationOption::OnDemandOnly:
// OnDemandOnly will parse function as they are require to continue the
// execution on the main thread.
MOZ_CRASH("OnDemandOnly should not create a DelazificationContext.");
break;
case JS::DelazificationOption::CheckConcurrentWithOnDemand:
case JS::DelazificationOption::ConcurrentDepthFirst:
// ConcurrentDepthFirst visit all functions to be delazified, visiting the
// inner functions before the siblings functions.
strategy_ = fc_.getAllocator()->make_unique<DepthFirstDelazification>();
break;
case JS::DelazificationOption::ConcurrentLargeFirst:
// ConcurrentLargeFirst visit all functions to be delazified, visiting the
// largest function first.
strategy_ = fc_.getAllocator()->make_unique<LargeFirstDelazification>();
break;
case JS::DelazificationOption::ParseEverythingEagerly:
// ParseEverythingEagerly parse all functions eagerly, thus leaving no
// functions to be parsed on demand.
MOZ_CRASH(
"ParseEverythingEagerly should not create a DelazificationContext");
break;
}
if (!strategy_) {
return false;
}
// Queue functions from the top-level to be delazify.
BorrowingCompilationStencil borrow(merger_.getResult());
ScriptIndex topLevel{0};
return strategy_->add(&fc_, borrow, topLevel);
}
bool DelazificationContext::delazify() {
fc_.setStackQuota(stackQuota_);
auto purgePool =
mozilla::MakeScopeExit([&] { fc_.nameCollectionPool().purge(); });
using namespace js::frontend;
// Create a scope-binding cache dedicated to this delazification. The memory
// would be reclaimed when interrupted or if all delazification are completed.
//
// We do not use the one from the JSContext/Runtime, as it is not thread safe
// to use it, as it could be purged by a GC in the mean time.
StencilScopeBindingCache scopeCache(merger_);
LifoAlloc tempLifoAlloc(JSContext::TEMP_LIFO_ALLOC_PRIMARY_CHUNK_SIZE);
while (!strategy_->done()) {
if (isInterrupted_) {
isInterrupted_ = false;
break;
}
RefPtr<CompilationStencil> innerStencil;
ScriptIndex scriptIndex = strategy_->next();
{
BorrowingCompilationStencil borrow(merger_.getResult());
// Take the next inner function to be delazified.
ScriptStencilRef scriptRef{borrow, scriptIndex};
MOZ_ASSERT(!scriptRef.scriptData().isGhost());
MOZ_ASSERT(!scriptRef.scriptData().hasSharedData());
// Parse and generate bytecode for the inner function.
DelazifyFailureReason failureReason;
innerStencil = DelazifyCanonicalScriptedFunction(
&fc_, tempLifoAlloc, initialPrefableOptions_, &scopeCache, borrow,
scriptIndex, &failureReason);
if (!innerStencil) {
if (failureReason == DelazifyFailureReason::Compressed) {
// The script source is already compressed, and delazification cannot
// be performed without decompressing.
// There is no reason to keep our eager delazification going.
strategy_->clear();
return true;
}
strategy_->clear();
return false;
}
// Add the generated stencil to the cache, to be consumed by the main
// thread.
DelazificationCache& cache = DelazificationCache::getSingleton();
StencilContext key(borrow.source, scriptRef.scriptExtra().extent);
if (auto guard = cache.isSourceCached(borrow.source)) {
if (!cache.putNew(guard, key, innerStencil.get())) {
ReportOutOfMemory(&fc_);
strategy_->clear();
return false;
}
} else {
// Stencils for this source are no longer accepted in the cache, thus
// there is no reason to keep our eager delazification going.
strategy_->clear();
return true;
}
}
// We are merging the delazification now, while this could be post-poned
// until we have to look at inner functions, this is simpler to do it now
// than querying the cache for every enclosing script.
if (!merger_.addDelazification(&fc_, *innerStencil)) {
strategy_->clear();
return false;
}
{
BorrowingCompilationStencil borrow(merger_.getResult());
if (!strategy_->add(&fc_, borrow, scriptIndex)) {
strategy_->clear();
return false;
}
}
}
return true;
}
bool DelazificationContext::done() const {
if (!strategy_) {
return true;
}
return strategy_->done();
}
size_t DelazificationContext::sizeOfExcludingThis(
mozilla::MallocSizeOf mallocSizeOf) const {
size_t mergerSize = merger_.getResult().sizeOfIncludingThis(mallocSizeOf);
return mergerSize;
}